The remains of a dying star look like a puff of cotton candy in this infrared image from Spitzer Space Telescope. Known as NGC 4361, the star is classified as a planetary nebula because of its superficial resemblance to a planet. It has expelled its outer layers of gas, which are expanding into space at thousands of miles per hour. The star's hot core, a white dwarf, illuminates the surrounding nebula. [NASA/JPL]
A star is both bright and a little dull: It's bright enough to shine across vast cosmic distances, but about as exciting to look at as a bare light bulb.
Until it reaches the final stages of life, that is. Then, like a butterfly emerging from its chrysalis, it dazzles the eye with not just its brilliance, but its beauty. It expels its outer layers into space and sculpts them into shapes that resemble soap bubbles, hourglasses, atoms, and strands of DNA, colored in shades of yellow, blue, orange, and red.
An example is in Corvus, the crow, whose brightest stars form a shape like a sail. It's low in the southeast at nightfall and floats across the south later on.
Telescopes reveal a small puff of light near the top of the sail that resembles a cottonball or a sprig of cotton candy. Known as NGC 4361, it's a planetary nebula -- a star that's in its death throes. Its outer layers of gas and dust are flowing out into space. The star's exposed core lights up this material, forming the bright nebula. It may be sculpted in part by the gravity of a smaller companion star, forming a thick disk around the dying star's waist.
In a few tens of thousands of years, the nebula will dissipate and fade from view. But others will take its place. In fact, the stars that outline Corvus's "sail" all face that same future, and some of them in the relatively near future -- astronomically speaking, that is: sometime in the next few million years.
Script by Damond Benningfield, Copyright 2011
For more skywatching tips, astronomy news, and much more, read StarDate magazine.